A&P I - Chapter 15: Equilibrium
Hair cells in anterior, posterior, and lateral semicircular ducts of membranous labyrinth
detect changes in dynamic equilibrium, including angular and rotational movements of head
ampulla in urticle
each duct is connected to
ampulla
enlarged region
stereocilia bend toward kinocilium
hair cells depolarize and release more glutamate; increases number of action potentials produced in axons of vestibular nerve
stereocilia bend away from kinocilium
hair cells hyperpolarize and release less glutamate; reduces number of action potentials formed in axons of vestibular nerve
Stereocilia in saccule
horizontally oriented when head is upright and stationary
Utricle and saccule
segments of membranous labyrinth located in vestibule, both contain a macula
maculae
sensitive only to changes in rate of movement, not movement itself
vestibular nuclei
vestibular signals travel to
endolymph and otolithic membrane in vestibule
; bends stereocilia; depending on direction, this either increases or decreases neuron activity, which brain interprets as body accelerating
beginning of head rotation
Brain interprets change in nerve activity as
muscle movement, cognitive awareness, compensatory eye movement
Responses to vestibular input can be grouped into following categories
endolymph and otolithic membrane continue to move forward
When hair cells and rest of body come to a stop
opposite
When head stops moving endolymph continues to move, bending cupula in direction ______________ of direction head was moving
crista ampullaris
a gelatinous mass where a cluster of hair cells with stereocilia and a solitary kinocilium are embedded
Maculae pairing
allows brain to determine which direction head is tilting
Stereocilia in utricle
bend in response to tilting head side to side or front to back
Stereocilia in saccule
bend in response to up and down movements of head
alters, activity
bending stereocilia _________release of inhibitory neurotransmitter glutamate; alters _________ of vestibular neurons
endolymph and otolithic membrane
bends hairs in direction opposite and activity of vestibular neurons changes accordingly
Otoliths
calcium carbonate crystals found in otolithic membrane increase membrane density
Macula
contains receptor cells for head position and movement
otolithic membrane
gelatinous mass where kinocilium and sterocilia are embedded
vestibular system
includes vestibule and semicircular canals
equilibrium
inner ear contains organs that detect two types of
utricle and saccule
involved in detecting linear acceleration; form of dynamic equilibrium
vestibular nuclei
located at medulla-pons junction
stopped
opposing movement effect has opposite effect on glutamate release and activity of vestibular nerve; signals that head has _________ moving
semicirucular ducts
oriented to detect rotation in all three body planes; contain endolymph
Static equilibrium
maintaining balance when head is tilted but head and body are not moving
Dynamic equilibrium
maintaining balance when head or body is undergoing rotational or angular motions (such as spinning in a rotating chair) or linear acceleration (such as riding in a car)
endolymph and otolithic membrane in vestibule
movement lags behind that of hair cells in wall of utricle and saccule
motion sickness
occurs when brain receives mismatched sensory information from eyes and vestibular system
vestibular sesnation
provides information about head position and movement
hair cells
release neurotransmitter glutamate continuously onto dendrites of bipolar neurons that form vestibular division of CN VIII
motion sickness
symptoms such as nausea, dizziness, and sometimes vomiting; can occur during particular types of movement
cerebellum, spinal cord, coordinate muscle movement
vestibular nuclei forward signals simuataneously to ___________ and __________ to ______________________ that maintains balance in response to head movement
maculae pairing
tilting your head in one direction polarizes hair cells in one ear and hyperpolarizes hair cells in other ear
kinocilium
true cilium that is taller than stereocilia
Stereocilia in utricle
vertically oriented when head is upright and stationary
thalamus, inferior parietal lobe, conscious awarness
vestibular nuclei forward signals simuataneously to _________ and ___________ for ___________ of head position and movement
cranial nerve nuclei, coordinate eye movement
vestibular nuclei forward signals simuataneously to _________ associated with extrinsic eye muscles to ______________________ in response to head movement
stereocilia bends
when gravity pulls on otolithic membrane
endolymph; cupula
when head is turned __________ lags behind and pushes on _________
pulls on otolithic membrane
when head tilts, gravity
